Devise or design an assay for detecting genetic damage or changes that may increase the rate of damage in mammary cells. General possibilities for assessing genetic damage might be the enumeration of cells with mutant phenotypes, determination of induced damage to DNA of individual cells or of populations of cells, or the enumeration of cells with evidence of mitotic disturbances. Such an assay would then be used to study the effects of age, diet, hormones, carcinogens, etc., on the incidence of genetic damage.